There has been known a greenhouse framework having a pillar erected on a foundation, a principal rafter rigidly joined to the upper end of the pillar, a ridge beam supported on the principal rafter, and a purlin fixed onto the principal rafter in parallel with the ridge beam.
A roof frame constructing such greenhouse framework has the principal rafter, ridge beam, and purlin. Typically, each of these members is carried to the top of the pillar erected on the foundation using a crane to be built.
The lifting workload for carrying these members to a high place is significantly large. Building at a high place requires a high technique for an operator and is greatly inefficient and dangerous as compared with building it on the ground. The principal rafter needs to be rigidly joined to the pillar using a large number of bolts. There are numerous joints in building the roof frame. Considerable time and effort are required and the building cost is high.
There has been a conventional greenhouse framework called Dutch Light type. Such greenhouse framework is formed in such a manner that a girder is rigidly joined between pillars erected in the width direction to build a roof frame having a ridge beam, a purlin, and a rafter between girders in parallel in the depth direction.
In such greenhouse framework, the strength of the roof frame is insufficient to a lifting load acting on the roof surface when a strong wind blows so that the roof frame can be easily destroyed. In addition, in such greenhouse framework, each member constructing the roof frame is carried to the top of the pillar erected on a foundation using a crane to be built. The lifting workload is significantly large. The building requires a skilled operator. Building at a high place is inefficient and dangerous for even the skilled operator. There are numerous joints in building the roof frame. Considerable time and effort are required and the building cost is high. Further, in such greenhouse framework, a vertical load acting on the roof is concentrated onto the purlin bridged between the girders. The space between the pillars in the depth direction is limited to be small.
In view of the problem of greenhouse building that many kinds of members are carried to a constructing site to be built, there has been proposed that the length and shape of members necessary for greenhouse building such as a pillar, a beam, a ridge beam, and a rafter are designed in modules (for instance, see Japanese Patent Application Laid-Open No. 2002-291348).
In the greenhouse framework construction itself as conventional, when the length and shape of the pillar, the beam, and the like are designed in modules to build a roof frame, each of these members need to be lifted to a high place to be built there. The building requires a skilled operator. The building at a high place is inefficient and dangerous for even the skilled operator. There are numerous joints in building the roof frame. Considerable working time is required and the building cost is high.    Patent Document 1: JP, 2002-291348, A